The importance of temperature control and adequate ventilation has long been known in the field of livestock and poultry buildings. Animals raised in these buildings require a constant supply of fresh air for growth and development. As the number of animals confined increases or their relative size increases, additional air must be introduced into these confinement buildings.
The close proximity of animals in a confinement building generates large amounts of fecal waste material and heat. Although these confinement buildings are often equipped with a means for the easy removal of waste material, a constant supply of moving air is necessary for animal health. The spread of communicable diseases common in confinement operations and can lead to devastating losses to the poultry or livestock producer. A constant supply of fresh, quality air inhibits the generation and spread of such diseases.
An efficient conversion of feedstuff into marketable protein and fat products is of paramount importance to a poultry and livestock producer. Unreliable air quality can result in animals with physiological stress from expending metabolic energy for respiration and controlling core body temperature. These animals tend to gain weight at a lower rate than animals raised in less stressful environments. An animal's production of eggs and milk will also decrease in response to elevated stress. Slower rates of gain and lower production increase the costs to the producer thus lowering his profits.
In a given confinement building, a certain amount of air must be replaced. This is done in order to remove moisture, by-products of respiration, and dust and to bring in a sufficient amount of fresh air. However, it is important that the air be brought in in a way as to protect the livestock. Cold air is normally dryer and contains more oxygen per cubic foot than warm air. In fact, for every 20 degrees Fahrenheit, air expands two to one. Therefore, less cold air is required than warm air to accommodate the livestock in a confinement building. Keeping that in mind, it is also necessary to prevent incoming cold air from just dumping onto the livestock in a building. This is done by increasing the velocity of the air as it enters the building. Air entering a building near the ceiling at 600 fpm will shoot over 20 feet in a building. If cold air is brought in at this sort of velocity, it is well mixed and warmed by the surrounding air before it reaches the livestock. However, in warm weather the opposite is true. It is necessary to bring in a larger volume (to bring in the same amount of oxygen and moisture carrying capability) of air to accomplish the necessary ventilation. Furthermore, because this air is warm, it is acceptable to bring it in at a low velocity and allow it to fall directly onto the livestock. Two methods exist with variable speed fans and the other is to have set speed fans with movable vent openings. The latter is what is most commonly used in livestock and poultry buildings because, with a static pressure monitor such as the Power Vent, control is position, that is, the system reacts to a direct measurement.
Livestock and poultry buildings must be well ventilated out of health concerns for the producer and or his/her employees. Without adequate ventilation, these buildings can be inundated with ammonia and excessive humidity. These gases are capable of entering a person's respiratory system and causing complications after prolonged exposure. Many confinement operations require the use of a mask to prevent the inhalation of these gases. A growing, nationwide concern for the safety of farm laborers makes improved ventilating techniques of vital importance.
Methods commonly used to bring air into confinement buildings include motorized baffles or vent doors. These baffles and doors can be opened at varying degrees to compensate for the number of exhaust fans running at any given time to force air out of a building. Mechanical controllers, such as the Hired-Hand Vent Controller, are used to open and close vent doors or raise and lower curtains via power drive units as needed.
The current systems for controlling air flow into a confinement building have relied only on an acceptable differential static pressure to open and close vents or curtains. These systems were not capable of changing the velocity of air entering the building with the change in the outside temperature. Often extremely cold air would be forced in directly over livestock before the ambient temperature inside the building was altered enough for a controller to halt the flow of air. These immediate sharp temperature gradients can cause the onset of sickness or death including pneumonia in some livestock. Present confinement ventilating systems are thus inadequate for controlling the velocity of air, contact of air with livestock and mixing of air upon entry into a confinement building.